1. Field of the Invention
The present invention relates to an onboard charging control apparatus which is mounted on a vehicle having a secondary battery being chargeable with off-board electricity and a motor driven by electric power of the battery and controls a charge to the battery.
2. Description of Related Art
In a type of vehicle, driving force required to run the vehicle can be obtained by driving a motor by electric power of a battery. Especially, in a recent year, for the purpose of environmental protection, conservation of resources, enhancement of fuel economy and the like, a vehicle with a motor-driving secondary battery being chargeable by an off-board (or external) power source such as a power source for domestic use has been proposed, and this vehicle has been already put to practical use.
As a type of vehicle having a secondary battery being chargeable with off-board electricity, for example, a plug-in hybrid vehicle (PHV) being able to obtain a driving force from both an engine and a motor, an electric vehicle (EV) obtaining a driving force only from a motor, and a fuel battery electric vehicle (FC) are well known. As a secondary battery for driving a motor, a nickel hydrogen battery and a lithium ion battery are, for example, well known.
Further, in this type of vehicle, for the convenience of users charging a secondary battery by off-board electricity, for example, a charging method has been improved to quickly charge the battery in a short time.
In contrast, when a quick charge is performed for the battery or when a battery fully charged is left as it is for a longtime without being used, it is well known that the battery life is considerably shortened. Therefore, it is important to provide a method and an apparatus for charging a secondary battery with off-board electricity while lengthening the battery life and maintaining the convenience of a user when charging.
Published Japanese Patent First Publication No. 2009-254221 discloses a technique as a charging method executed without shortening the battery life. In this technique, a user of a vehicle can manually set a date at which the user plans to drive the vehicle at the next time. When the user sets a date of the next driving at an end time of the current driving, a preliminary charge is performed for a battery to set the state of charge (SOC) in the battery at a predetermined level, and then a primary charge is performed for the battery at the night earlier than the next driving date to set the battery in the fully-charged state. Therefore, the period of time in which the battery is set in the fully-charged state can be shortened, so that the shortening of the battery life can be prevented.
However, in the technique disclosed in this Publication, it is required that the user himself or herself manually inputs a next driving date to the vehicle to set the date. Therefore, unless the user sets a next driving date after the completion of the current driving, the primary charge to the battery is immediately performed in response to the insertion of a plug of an off-board power source into the vehicle, and the battery is set in the fully-charged state. As a result, because there is a high probability that the battery fully charged is left for a long time without being used, the battery life is undesirably shortened at high probability.